ES2401082T3 - Fiber optic shunt cables - Google Patents

Abstract

Fiber optic cable (10; 40; 60) comprising a cladding (19) having a first portion (20) and a second portion (22), and means (26) for separating the first and second portions (20, 22) , said first portion (20) comprising a wall defining at least one passage (23; 44; 63) for one or more optical fibers (11) and said second portion (22) containing a plurality of electrical conductors (12); in which the cable (10; 40; 60) is a drop cable for suspension installation and in which the first portion (20) contains a reinforcing arrangement (28) made of a dielectric material encapsulated in the wall, to supporting the cable (10) in a suspension installation (100), in which said reinforcing device comprises reinforcing elements separated from each other (28) extending in the longitudinal direction of the first portion (20), said reinforcing elements comprising two reinforcing elements (28) arranged in opposite spaced relationship and in which the or each of said passages (23; 44; 63) is arranged therebetween, in which said first portion (20) has a longitudinal axis, said second portion (22) a longitudinal axis and said two reinforcing elements (28) being arranged in a plane that first passes through the longitudinal axis of said first portion (20), said first plane being perpendicular to a plane passing through d e said second longitudinal axis, and in which said first and second portions (20, 22) of the liner (19) each have a generally circular cross-section, with a third mesh or thickening portion (24) connecting said first portion (20 ) and said second portion (22) and said portions (20, 22) being arranged such that said liner (19) has a cross section that is substantially in the shape of a number 8, with a connecting mesh or a third thickening portion (24), wherein the separation means comprise a separation arrangement (26) to facilitate selective separation of said first and second portions (20, 22) of the liner (19), said separation device comprising a tear element (26 ) housed in said third portion (24) of liner (19) between said first portion (20) and said second portion (22) for tearing through said liner (19) to facilitate separation s of said first and second portions (20, 22) of the liner (19), wherein said first portion (20) has a longitudinal axis, said second portion (22) has a longitudinal axis, and said tear element (26) is displaced with respect to a plane passing through said axes, whereby when separated, the first and second portions (20,22) maintain their generally circular cross section.

Description

Fiber optic shunt cables

The present invention relates to fiber optic bypass cables for use in telecommunications systems and, in particular, but not exclusively, to said cables for use in the connection between a customer's premises and a common connection point for A number of such customers.

In the field of telecommunications networks, cables typically extend from an exchanger to a closet mounted at street level, and from this closet the cables are routed to a customer's premises, usually through an installation aerial, or suspended, comprising a cable suspended in catenary from poles or around buildings. These overhead cables that lead to the customer's facilities are known as the final branch cable.

Historically, a final branch cable has normally comprised a number of insulated conductor cables contained in a sheath. More recently, the development of optical fibers has made it necessary to replace the shunt cables with optical fibers, since the latter can transmit much more data. However, it is also desirable that the bypass cable must carry an electrical supply so that a telephone connected to the bypass cable can be used in emergency situations when the power supply network has been interrupted to the premises where The phone is located. For this reason, it is desirable for a branch cable to include one or more optical fibers and a pair of insulated copper conductor cables.

Applicant application GB-A-2270992 discloses a cable containing electrical conductors and separable optical fibers. The cable comprises electrical energy conductors for transporting voltage supplies from the electrical network, a plurality of optical fibers and the coating of the conductors and the fibers. The coating is in the form of a figure of eight and defines two separate chambers, one for electrical conductors and the other for optical fibers. However, this cable is designed for underground routing and not for suspended installation. In addition, it is not suitable for the realization of a relatively low voltage power supply for powering a telephone or otherwise as an end lead cable.

Patent publication US-A-5 189 718 discloses a fiber optic cable.

Patent publication EP-A-0 780 713 discloses a suspended installation for fiber optic cables.

Patent Publication US-5 960 144 refers to a communications cable having a cable core and an outer sheath with strain relief elements in the outer sheath. Four stress relief elements are arranged in pairs that are symmetrical around a plane of flexion.

The invention relates to a fiber optic shunt cable according to claim 1.

In order that the invention may be well understood, some embodiments thereof will now be described with reference to the drawings, in which:

Figure 1 is a schematic cross section of a fiber optic shunt cable comprising an optical fiber and electrical conductors;

Figure 2 is a schematic cross section of a fiber optic shunt cable containing a plurality of optical fibers and electrical conductors;

Figure 3 is a schematic cross section of a fiber optic shunt cable comprising an optical fiber and electrical conductors; Y

Figure 4 is a schematic representation of a branch cable installation that includes a cable as shown in Figure 1, 2 or 3;

Figure 5 is an enlargement of the portion of Figure 4;

Figure 6 is a schematic representation of a connection box of the installation of Figure 4, and

Figure 7 shows an arrangement of a pressure adjustment connector included in the connection box.

Figure 1 shows a fiber optic shunt cable 10 containing a dampened optical fiber 11 and two insulated electrical conductors 12. The dampened optical fiber 11 comprises an optical fiber 13 and a plastic sheath 14 that protects the surface of the fiber 13 of scratching and abrasion. The plastic coating can be for example a nylon coating and the fiber with coating will typically have a diameter of approximately 1 mm. The insulated conductors 12 comprise copper cables 16 encapsulated in an insulating electrical coating with color coding 18, which can be of any suitable material as will be well known to those skilled in the art. Typically, copper wires will have a diameter of approximately 0.4 mm and the outer diameter of the insulating sheath will typically be approximately 1.2 mm. An insulated conductor 12 serves as the conductor wire and the other as a neutral / ground wire in a circuit that usually takes 9 to 12 volts to power a telephone connected to the cable. It is to be understood that copper wires are given only as an example and that any suitable conductive material, such as aluminum, could be used instead.

The optical fiber 11 and the electrical conductors 12 are housed in the lining 19, which comprises a first portion 20 containing the optical fiber 13 and a second portion 22 which is separable from the first portion and containing the electrical conductors 12. The fiber Optic 11 is in a passage 23 defined by the first portion 20 with the wall defining the passage circumferentially coupling the optical fiber along the length of the fiber.

The coating portions 20, 22 are substantially circular in cross-section and in parallel side-to-side relationship to define a shape that approximates a number 8. At the point of connection between the coating portions, there is a thickening, or mesh 24 The mesh houses a tear 26, or opening cord, which is displaced with respect to a plane that passes through the longitudinal axes of the first and second sheath portions and runs along the cable substantially parallel to said axes. . The opening cord 26 can be made of any material strong enough to open through the mesh 24 before the application of a tear force in order to allow the separation of the first and second lining portions. A suitable material for the opening cord is a high strength Terylene (TN) rope. The coating 19 may be made of any suitable coating material, such as polyethylene, MDPE, HDPE or nylon. Typically, the first portion 20 of the coating having a diameter of approximately 8 mm and the combined height of the two coating portions would be approximately 12 mm.

A reinforcing arrangement is provided in the first portion 20 of the lining in the form of reinforcing elements 28 disposed adjacent to the optical fiber 11. The reinforcing elements 28 are arranged in separate parallel relationship, one on each side of the optical fiber 11 and encapsulated in the first portion 20 of the coating. As shown in the drawing, the reinforcing elements are preferably arranged in a plane that extends perpendicular to a plane that passes through the respective longitudinal axes of the lining portions 20, 22 and along the longitudinal axis of the first portion 20 of the coating. The reinforcing elements 28 have a substantially circular shape in their cross-section and generally extend parallel to the longitudinal axis of the first portion 20 of the coating.

Preferably, the reinforcing elements are made of a dielectric material such as glass reinforced plastic (GRP), although glass fibers can be used with similar advantage. Other non-preferred materials include aramid fibers. GRP reinforcement materials are a preferred material since the material has a coefficient of thermal expansion similar to optical fibers and therefore changes in the length of the reinforcement elements, due to thermal effects, should not give rise to an increase in the forces transmitted to the optical fiber. Glass fibers offer a similar advantage. Materials such as aramid fibers and metal elements have a coefficient of thermal expansion different from the optical fibers and if used, the fact that they will expand or contract differently from the optical fibers must be taken into account and measures must be taken to ensure that this does not result in an adverse load on the optical fiber 13.

Other advantages are obtained by having reinforcing elements made of an electrically non-conductive material, such as GRP, fiberglass or aramid. If the reinforcing elements are made of an electrically conductive material such as a braided steel, it is necessary to increase the diameter of the coating for electrical insulation purposes. When electrically non-conductive reinforcing elements are used, there is no requirement to maintain a greater coating thickness in the first portion 20 of the coating in order to satisfy any tensile strength requirement. Thus, the diameter of the first portion of the coating can be reduced, which reduces the effect of wind and ice loads on the cable. It is believed that by using electrically non-conductive reinforcing elements, the diameter of the first portion 19 of the coating can be reduced by up to 2 mm compared to the case in which the coating is required to provide electrical insulation.

The fiber optic shunt cable 40 shown in Figure 2 shows modifications that can be made to the optical shunt fiber 10 individually or in combination. The first modification comprises the addition of two additional reinforcement elements 28. The four reinforcement elements 28 of the fiber optic cable 40 are arranged in a common separation circle and are separated at 90 ° intervals over the circle, so that a plane passing through the longitudinal axes of the first and second portions 20, 22 of the lining passes through the longitudinal axis of two of the reinforcing elements and a second plane perpendicular to the plane passing through the longitudinal axes of the other two elements of reinforcement. The second modification comprises the provision of two optical fibers 11. As shown in the drawing, the optical fibers 11 are weakly located in a circular passage 44. However, the first portion 20 of the coating may be formed to define a single passage or separate passages enclosing the optical fibers in the same manner as in the fiber optic cable 10 in Figure 1.

Figure 3 shows an optical fiber bypass cable 60 that differs from the optical fiber bypass cable 10 in that the optical fiber 11 is freely housed in a hollow plastic tube 62 contained in a passage 63 defined by the first sheath portion 20. This tube may contain more than one optical fiber, although only one is shown in the drawing.

A possible modification (not shown) to the derivation of the fiber optic cable 60 shown in Figure 3 comprises the omission of the optical fiber (s) 11 from the tube 62. In this case, one or more fibers 11 are blown into the tube after the installation of the fiber optic bypass cable. The optical fibers to be installed by blown fiber processes can, for example, take the form described in EP-A0345968, EP-A-0521710 or EP-A-0646818 and can be introduced into the tube 62 by blowing procedures known, such as the process described in EP-A-0108590. For the installation of blown fiber, the tube 62 may be made of polyethylene with a radially loaded carbon inner surface to increase the conductivity, as described in US4952021. The blown fiber installation has the advantage that the optical fiber (s) is not subject to stresses that arise during cable suspension.

Figure 4 shows a shunt installation 100 comprising any of the fiber optic shunt cables 10, 40 and 60. For ease of description, reference will now be made only to the installation comprising the fiber optic shunt cable 10.

The bypass installation 100 includes a housing 101 containing a distribution arrangement for the distribution of connections to the telecommunications lines that are to be extended to the customer's premises. The housing is fed from an exchanger by means of a multi-fiber optic fiber cable 102, such as a known underground fiber cable 48. A multi-fiber fiber optic cable 103 comprising fibers sufficient to connect with ten telecommunication lines 104 (ten fibers for single-fiber circuits or twenty fibers for twin-fiber circuits) is conducted from the housing 101 to a junction box , or manifold 105 of an adjacent pole 106. In addition, reference number 103 indicates electrical conductors to conduct a voltage of 9 to 12 volts to the manifold.

A telecommunications line 104 goes from the manifold 105 to the customer's facilities, such as a building

107. In the drawing, two telecommunication lines 104 are shown, one extending to the right of the collector and leading to building 107 and the other extending to the left of the collector. As mentioned earlier, the fiber optic cable 103 contains enough optical fibers to connect to ten telecommunication lines 104 and therefore there may be ten separate telecommunication lines extending from the manifold.

105.

Each of the telecommunication lines 104 comprises a plurality of lengths of fiber optic bypass cable 10 connected end to end in the respective connection boxes 108 mounted on posts 106 and building 107. Cable lengths 10 are connected to posts 106 by clamping devices

110. In the drawing, only two posts are shown, but in practice they will be as many posts as are required to support the cable in the path between the manifold 105 and the customer's facilities. Typically, the spacing between the posts is approximately 200 feet (61 meters), although it can be up to 100 meters.

As best seen in Figure 5, each clamping device 110 comprises an elongate member 112 that is folded to define two end portions 114, 116 that are helically wrapped around the first portion 20 of the liner in the same direction, and a curve, or loop, 118 that connects the end portions. The clamping device 110 further comprises a tensile connection element 120 having end hook portions, one of which couples the loop 118 and the other of which is coupled with a post ring 122 fixed to the post 106. The element Tensile connection 120 may include means (not shown) for adjusting the tension in the cable 10 between the clamping devices on adjacent posts 106. In this case, the tensile connection element may comprise two portions, each having a Thread at its ends away from the hook end portions and connected to each other by a nut so that the rotation of the nut causes the elongation or shortening of the tensile connecting element.

As shown in Figure 5, in order to allow the end portions 114, 116 of the elongate member 112 to be wrapped around the first portion 20 of the liner, the second portion 22 containing the electrical conductors 12 separated from the first portion 19. This separation is easily obtained by accessing the free end of the tear cord 26 at the adjacent end of the fiber optic cable 10 and using this to tear through the mesh 24 at a suitable distance. In the drawing a break is shown in the separate portion of the first portion 19 of the lining simply to allow a better view of the loop 118 and the traction connection element 120.

As shown schematically in Figure 6, a connection box 108 has a hollow interior 130, which can be accessed by removing a cover plate (not shown). An opening 132 for a cable 10 is provided on each side of the box to serve as an entry point for one end of a cable 10. As an alternative to individual openings 132, pairs of openings can be provided individually to receive portions of the separate lining. The connection boxes 108 are fixed to the posts 106 by any suitable means, such as screws 133. Each box contains a pressure adjustment connector arrangement, or device, 134 by means of which the ends of the cables 10 are secured. inside the box. The pressure adjustment connector arrangement 134 can use any known suitable pressure adjustment technology and has two pressure adjustment connection points 135 in separate positions, one for each end of the cable.

The pressure adjustment connection points 135 can each include two pressure adjustment connectors, such as the pressure adjustment connector 136 as shown in Figure 7. Each pressure adjustment connector 136 comprises a body 138 which defines a stepped through passage 140. Gripping means 142 comprising a ring having a plurality of radially spaced apart projections or spikes that extend axially inwardly, is housed in a larger diameter portion 144 of the through passage 140 in a position away from the ends of the through passage. The gripping means 142 are preferably made of metal, but may be made of a plastic material, and the barbs are capable of radially deflecting outwards at the insertion of one end of a coating portion 20, 22 in the through passage 140 ( from the right as seen in the drawing), but they are embedded in the sheathing if the cable is pulled in the opposite direction to the direction of insertion in order to resist subsequent removal of the sheath portion of the connection point 135. A clamp 146 can be provided to allow removal of the coating portion if it is desirable to break the connection. The clamp 146 has a cylindrical front end portion 148 projecting in the through passage 140 and can be coupled with the spikes moving inwardly axial with respect to the gripping means 142 to deflect the spikes radially outward to release the grip on the lining portion and allow its removal.

To form a connection between the adjacent ends of the cable lengths 10 in a connection box 108, the separate first and second sheath portions 20, 22 of the respective ends of the cables passing through the openings 132 inside gap of the junction box 108. The cladding and reinforcing elements 28 are cut back to expose the optical fiber 11 and the insulated conductors 12 and then the ends of the cladding portions are snapped into the respective fitting connectors at pressure 136 until the cut end of the liner is supported by an edge 150 defined by the passage 140. At this stage, the ends of the first and second portions of the liner that are fastened on the pressure adjusting connectors 136 by the spikes of the gripping means 142 and the exposed optical fiber 11 and the insulated conductors 12 protrude from the inner ends 152 of the s through passages to a connection region 154 of the connection box. Here, the electrical conductors and optical fibers of the cable ends are connected by any suitable conventional means. For example, the conductors 12 may be connected by re-extracting the insulating layer 18 to expose the copper wires 16 and twisting the ends of the wires together. Alternatively, a terminal block can be used in which the ends of the conductive cables are fixed by means of screws.

The manifold 105 may be similar in construction to a junction box 108. The manifold 105 could contain an additional opening through which the fiber optic cable 103 and ten openings 132 are fed to allow ten telecommunication lines 104 to feed from the collector. The ends of the telecommunication lines 104 can be secured in the manifold 105 by means of pressure adjustment connectors, such as pressure adjustment connectors 136 in the same manner as in the junction boxes 108, or by any other means suitable. Similarly, the connections between the electrical conductors that are fed into the collector and the optical fibers of the optical fiber 103 can be made with the electrical conductors 12 and the optical fibers 11 by any suitable conventional means. As shown in FIG. 4, the lengths of fiber optic bypass cable 10 suspended between posts 106 are connected to the posts of the clamping devices 110, which are fixed to the cable in positions separated at a distance from their ends. The tension in the cable suspended between the posts can be adjusted after the suspension of the cable by means of the adjustment means of the traction connection elements 120 provided such means are provided. The end portions 10E (Figure 5) of the first portion of the liner and its contents between the clamping devices 110 and the connection boxes 108 are distended.

The helical winding of the ends 114, 116 of the elongate member 112 can be adapted such that it holds the sheath with a predetermined force so that the sheath will slip when the tension in the cable 10 reaches or exceeds a predetermined level. Once the cable slides, the previously non-tensioned portions 10E will be tensioned and the connection points 136 are arranged such that the cable will be released, breaking the connection with the adjacent cable lengths when the tension in the portion 10E reaches a second predetermined level that is not greater than the tension load that causes the cable to slip and is preferably substantially less. The tension load in which the elongate element 112 allows the cable to slide is selected such that the cable slides at a lower load than that required to break the cable. It is expected that the force of the cable is such that it breaks under a load in the region of 2KN, that the elongate element 112 is arranged to allow the cable to slide under a load in the region of 1.2 to 1.5KN and the Pressure adjustment connectors are arranged to allow cable connections to break with a load in the 170N region, although it should be understood that these loads are given as examples and should not be taken as limiting.

In the bypass installation 100, the ends 10E are described being fixed to the connection box 106 by means of a pressure adjustment arrangement. It will be appreciated that this arrangement, although advantageous in terms of simplicity and ease of assembly, should not be taken as limiting. The ends 10E can be secured by any suitable means, such as an elastic cable clamp that provides sufficient security to hold the ends 10E in place and prevent any tensile load from being transmitted to the joints between the optical fibers 11 and the conductors. 12 during normal operating conditions and at the same time allow the breakage of the connection to a tensile load not greater than that required to cause the cable to slip through the clamping devices 110.

If the telecommunications line 104 is constructed using a fiber optic bypass cable 60 as shown in Figure 3, the optical fiber (s) being installed by the blown fiber technique, it is necessary to provide a passage substantially impermeable to gases along which the optical fibers are going to be blown. In this case, the first portion 20 of the liner is trimmed so that when its end is snapped into a pressure fitting connector 136, the cut end of the plastic tube 62 protrudes from the end 152 of the through passage 140 in the connection region 154. The ends of the tubes 62 protruding in the connection region can then be interconnected to provide a gas-tight passage for the optical fiber (s) by means of a suitable length of tube inserted between them. Alternatively, means defining a passage between pressure fitting connection points 135 and arranged such that the ends of the tubes 62 can be inserted therein could be provided to provide a hermetic continuous passage for the fiber (s) (s) optics (s).

It should be understood that, although fiber optic shunt cables are described as being used in the shunt installation 100, which establishes a controlled break in the telecommunications line, this is not essential and the cables could be used in any conventional shunt installation. adequate.

Although it is not essential that the fiber optic shunt cables 10, 40, 60 are installed in an arrangement such as arrangement 100 that provides for the controlled breakage of the telecommunications line under a load less than that required to break the cable, You will appreciate that such an arrangement is advantageous. This is because the load that will cause the fiber optic bypass cable to slide and the connection between adjacent ends to break can be chosen to be less than that required to break the cable, which is a useful safety feature in the case of a tall vehicle that leads to telecommunication lines 104 or a tree or other structure that falls on it. In addition, since the connections between a length of the fiber optic bypass cable and adjacent line lengths are broken in the case of such events, damage to the telecommunications line must be located which reduces the time required and the repair cost. In addition, since the telecommunication line can be designed to break under the application of a predetermined load, the cable can be made significantly stronger than it might otherwise be, thus providing greater protection for the (s). ) optical fiber (s) contained in the cable. In particular, the cable can be made more rigid and therefore able to better withstand the effects of variable load due to the force of the wind and the moisture deposit or the formation of ice.

It will be understood that there are generally advantages of having the reinforcement arrangement provided in the first portion of the sheath adjacent to the optical fibers as opposed to the possibility of supporting the cable by means of an existing aerial installation, or by providing an auxiliary arrangement to reinforce the cable or in the second portion of the sheathing These are that the reinforcing arrangement can directly control the thermal performance and tensile strength of the cable and provide better protection for the optical fiber (s) by virtue of its close proximity to them. It also provides the advantage that if the coating portions are to be separated for installation in an arrangement such as that shown in Figures 4 and 5, no special measures need to be taken to protect the optical fiber (s) (s) in the region where the lining portions are separated.

The fiber optic shunt cables of the embodiments are low fiber count cables intended for use in aerial installations as a final shunt cable. It is envisioned that this type of low fiber count cable may comprise only one or two optical fibers. In addition, electrical conductors are intended to carry only a low voltage, preferably in the region of 9 to 12 volts, and only two conductors are necessary for this purpose.

Claims (16)

1. Fiber optic cable (10; 40; 60) comprising a sheath (19) having a first portion (20) and a second portion (22), and means (26) for separating the first and second portions (20 , 22), said first portion (20) comprising a wall defining at least one passage (23; 44; 63) for one or more optical fibers (11) and said second portion (22) containing a plurality of electrical conductors (12 ); wherein the cable (10; 40; 60) is a branch cable for installation in suspension and in which the first portion (20) contains a reinforcement arrangement (28) made of a dielectric material encapsulated in the wall, for supporting the cable (10) in a suspension installation (100), in which said reinforcement device comprises reinforcement elements separated from each other (28) extending in the longitudinal direction of the first portion (20), said means comprising reinforcement elements two reinforcement elements (28) arranged in opposite separate relationship and in which the or each of said passages (23; 44; 63) is arranged between them, in which said first portion (20) has a longitudinal axis, said second portion (22) having a longitudinal axis and said two reinforcing elements (28) being arranged in a plane that first passes through the longitudinal axis of said first portion (20), said first plane being perpendicular to a plane passing through said second longitudinal axis, and wherein said first and second portions (20, 22) of the lining (19) each generally have a circular cross-section, with a third mesh or thickening portion (24) connecting said first portion (20) and said second portion (22) and said portions (20, 22) being arranged such that said coating (19) has a cross section that is substantially in the form of a number 8, with a connecting mesh or a third thickening portion (24), in which the separation means comprise a separation arrangement (26) to facilitate the selective separation of said first and second portions (20, 22) of the coating (19), said separation device comprising a tear element (26) housed in said third portion (24) of the coating (19) between said first portion (20 ) and said second portion (22) for tearing through said liner (19) to facilitate selective separation of said first and second portions (20, 22) of the liner (19), wherein said first portion (20) it has a longitudinal axis, said second portion (22) has a longitudinal axis, and said tear element (26) is displaced with respect to a plane passing through said axes, whereby when they are separated, the first and s Second portions (20, 22) maintain their generally circular cross-section.

2.

 Cable (10) according to claim 1, having at least one of said passages (23) containing at least one optical fiber (11) that has a length and is circumferentially coupled along said length of said wall.

3.

 Cable (40; 60) according to claim 1, having at least one of said passages (44; 63) having at least one optical fiber (11) freely housed therein.

Four.

 Cable (60) according to claim 1, having at least one passage (63) containing a tubular element (62) to receive at least one optical fiber (11).

5.

 Cable (10; 40; 60) according to any one of the preceding claims, wherein said reinforcing arrangement

(28) comprises a glass reinforced plastic material.

6.

 Cable (10; 40; 60) according to any one of the preceding claims, comprising a housing for the optical fibers (11).

7.

 Cable (10; 40; 60) according to claim 6, wherein said housing contains at least one optical fiber (11).

8.

Shunt installation (100) that includes a telecommunications line (104) comprising a fiber optic shunt cable (10; 40; 60) as claimed in any one of the preceding claims, suspended from a plurality of aerial locations separated.

9.

 Installation (100) according to claim 8, wherein said telecommunications line (104) comprises a plurality of lengths of said fiber optic cable (10; 40; 60) connected end-to-end in said aerial locations by respective connection devices (108), said telecommunications line (104) being fixed to each of said elevated locations by means of respective clamping devices (110) fixed to the line in two separate positions, such that the portion of the line between said positions are tensioned and comprise said connection device (108), said fixing devices being

(110) arranged to allow the transmission of a tensile load to a said tensioned portion of the line when a tensile load on the adjacent line thereof on each side of the elevated location reaches a predetermined first level, and said devices being of connection (108) arranged to cause the end-to-end connection of the fiber optic cable lengths (10; 40; 60) connected to break when the tensile load transmitted to said non-tensioned portion reaches a predetermined second amount, which is less than a tensile load required to break the fiber optic cable (10; 40; 60) and not greater than said first predetermined level.

10.

 Installation (100) according to claim 9, wherein each clamping device (110) is arranged to frictionically hold said liner (19) and to allow said line (104) to slide relative to it to transmit said load of traction.

eleven.

 Installation (100) according to claim 9 or 10, wherein said first and second portions (20, 22) of the cable lengths (10; 40; 60) are separated from each other in the respective regions of the cable lengths ( 10; 40; 60), in which the clamping devices (110) are coupled to the telecommunications line (104).

12.

 Installation (100) as claimed in claim 11, wherein the clamping devices (110)

5 comprise two end portions (114) of a double bent elongate element (112), whose end portions (114) are helically wrapped around the first portion (20) of the liner (19) in a respective region of separation in the that said first and second portions (20, 22) of the coating (19) have been separated. 13. Installation (100) according to claim 11 or 12, wherein the separation regions of the first and second 10 portions (20, 22) of the lining (19) extend to the respective connection device (108), in which the first and second portions (20, 22) are connected separately with the connection device (108).

14.

 Installation (100) according to claim 13, wherein said connection devices (108) comprise respective pressure adjustment connectors for the first and second portions (20, 22) of the liner (19).

fifteen.

 Installation (100) according to any one of claims 9 to 14 when dependent on claim 6 or

15 7, wherein in each said end-to-end connection, a portion defining a connection passage (140) is arranged such that said connection passage (140) extends between the ends of the respective housings of the cable lengths (10; 40; 60) to define a substantially gas-tight passage for the optical fibers (11). 16. Installation (100) according to claim 15, wherein said portions are a portion of the respective connection devices (108).